Attempting to click on a Exchange 2019 mailbox database throws the error: "Your request couldn’t be completed. Please try again in a few minutes."

Problem

You’ve just completed installing Exchange Server 2019 into an existing organization then proceed to create mailbox databases on the servers but notice that you receive the following error when you attempt to browse the mailbox databases:

error

Your request couldn’t be completed. Please try again in a few minutes.

Continuing to click around would display the following symptoms:

The right hand pane will display the Please wait… message, which will never complete:

The following error would also be displayed at times:

500

Unexpected Error :(

An error occurred and your request couldn't be completed. Please try again.

Browsing the event logs may does not reveal any useful errors such as the one below (this lead me down an unrelated path of checking attributes which did not contribute to the error):

The MaxActiveDatabases attribute on the Information Store object in Active Directory has not been configured.

Solution

I spent a whole evening troubleshooting this issue without getting closer to the solution so I opened a call with Microsoft support. The engineer did not appear to have seen this before so she spent 2 full hours making changes to my account such as adding it to the Exchange Servers and Exchange Trusted Subsystem Groups (I questioned why these groups with computer accounts are even relevant), granting various accounts Full Control in the security tab of my account, asking to modify the Default Domain Policy setting Manage auditing and security logs to include the Exchange computer object groups (I had to stop her as I told her this would overwrite all of the computer objects in the directory), telling me I did not configure the Exchange server with 128GB of memory (argued with her that it was recommended, not required), and all sorts of actions I felt were not relevant.

Long story short, how she ended up getting to the resolution was something I can’t believe I did not try, and that is to move my admin mailbox to a mailbox database on the Exchange 2019 server. After moving the mailbox over and waiting for Active Directory to replicate, the mailbox databases displayed properly. It was a frustrating 2 hours but I’m glad she was able to get to the bottom of this and I hope she’ll write a KB about this so all the previous actions she made aren’t replicated with other engineers because anyone who has worked with Exchange for many years would become just as annoyed as I was.

Update – March 15, 2019

I started noticing the EAC / ECP displaying the same error at various times throughout the day even though my mailbox was moved over to the new server but what appears to consistently work is what a Hyili pointed out in this post:

Exchange 2019 - Issue with EAC (ECP) - error - your request couldn't be completed. Please try again in a few minutes
https://social.technet.microsoft.com/Forums/office/en-US/68a9d447-df76-4d2a-bddc-6ead33a6c044/exchange-2019-issue-with-eac-ecp-error-your-request-couldnt-be-completed-please-try-again?forum=Exch2019

I just found the solution to solve my problem. That is because the wrong ExchClientVer is used by EAC. EAC used to have ExchClientVer=15 in Exchange 2013, but it is currently using ExchClientVer=15.2 in Exchange 2019.

A quick solution is that we can just appending "ExchClientVer=15.2" directly to the EAC URL parameter. For example, the original url might be "https://<exchange_server_domain>/ecp/". After modification, new URL would be "https://<exchange_server_domain>/ecp/?ExchClientVer=15.2". In my case, everything looks FINE.

According to some articles about ExchClientVer, seems like it is decided by the location server of the admin mailbox. If the admin mailbox is located on the server with Exchange 2013, EAC would use ExchClientVer=15. So everything we need is to move our admin mailbox to the server with Exchange 2019. Just like terenceluk0925 have tried.

But unfortunately, moving the admin mailbox to the newer server did not work for me... I currently use the first tricky one.

I gave the URL format: https://<exchange_server_domain>/ecp/?ExchClientVer=15.2

… and go by navigating directly onto the server and using: https://localhost/ecp/?ExchClientVer=15.2 and can confirm that this workaround does indeed correct the issue.